Successful use of vegetable oils as environmentally friendly, that is, biodegradable, base fluids in industrial applications is contingent upon improving their low temperature viscometries. For example, a sunflower oil containing an oleic acid content of 80 percent has a pour point of -12.degree. C. and turns solid in the Brookfield viscosity measurement. Many of the industrial applications require a pour point of less than -25.degree. C. and a Brookfield viscosity of 7500to 110,000 centi Poises (cP) at -25.degree. C.
U.S. Pat. No. 3,598,736 (Van der Meij et al, Aug. 10, 1971 ) relates to soluble polyalkylmethacrylates which can be used in lubricating oil compositions to reduce the pour point. Within the polyalkylmethacrylate the alkyl group has from 10-20 carbon atoms and meets the following three requirements:
(1) The average number of carbon atoms of the alkyl chains in the methacrylates is between 13.8 and 14.8.
(2) The molar percentage of the alkyl methacrylates with branched alkyl chains is between 10 and 30.
(3) The molar percentage of the alkyl methacrylates with an odd number of carbon atoms in the alkyl chain is between 20 and 50.
These polymers are capable not only of considerably depressing the pour point of light lubricating oils, such a spindle oil and light machine oil, but show in addition a high activity as pour point depressants in heavy lubricating oils rich in residual components, such as heavy machine oil.
U.S. Pat. No. 3,702,300 (Coleman, Nov. 7, 1972) relates to a carboxy-containing interpolymer in which some of the carboxy radicals are esterified and the remaining carboxy radicals are neutralized by reaction with a polyamine compound having one primary or secondary amino group and is useful as an additive in lubricating compositions and fuels. The interpolymer is especially effective to impart desirable viscosity characteristics and anti-sludge properties to a lubricating oil.
U.S. Pat. No. 4,284,414 (Bryant, Aug. 18, 1981 ) relates to the use of mixed alkyl esters made by reacting two or more of certain monohydric alcohols with interpolymers which contain units derived from (i).alpha..beta.-unsaturated dicarboxylic acids, or derivatives thereof and (ii) vinyl aromatic monomers having up to 12 carbon atoms in crude oils. Minor amounts of the mixed alkyl esters are useful for modifying the fluidity and flow characteristics of crude oils, and more particularly, for improving the pipeline pumpability of crude oils.
U.S. Pat. No. 4,767,551 (Hunt et al, Aug. 30, 1988) relates to overbased copper-containing lubricant compositions with improved stability and antiwear and antirust properties wherein the overbased copper-containing composition inhibits the oxidation of the lubricant and preserves the antirust properties of the lubricant without significantly decreasing the antiwear properties of the zinc dialkyldithiophosphate antiwear additive during use of the lubricant in an operating engine. Further, this reference provides lubricating oil compositions containing a lubricating oil, a dispersant, a viscosity index improver dispersant, an antiwear agent and a dispersant/detergent, antioxidant and rust inhibitor comprising an overbased copper-containing composition which provides an improved lubricating oil formulation for high speed, high temperature gasoline and diesel engine operation.
U.S. Pat. No. 4,783,274 (Jokinen et al, Nov. 8, 1988) is concerned with an anhydrous oily lubricant, which is based on vegetable oils, which is substituted for mineral lubricant oils, and which, as its main component, contains triglycerides that are esters of saturated and/or unsaturated straight-chained C.sub.10 to C.sub.22 fatty acids and glycerol. The lubricant is characterized in that it contains at least 70 percent by weight of a triglyceride whose iodine number is at least 50 and no more than 125 and whose viscosity index is at least 190. As its basic component, instead of or along with the said triglyceride, the lubricant oil may also contain a polymer prepared by hot-polymerization out of the said triglyceride or out of a corresponding triglyceride. As additives, the lubricant oil may contain solvents, fatty acid derivatives, in particular, their metal salts, organic or inorganic, natural or synthetic polymers, and customary additives for lubricants.